I’m a fan of the Roller Delayed Blow Back firearms for a while and have had opportunities to own and shoot ones from HK, POF, and PTR. I knew the rollers were locking the bolt head in place but never really understood the details of the action. I’ve tracked down two great videos to help show you what is going on.
This is a PTR PDWR in .308 – basically a cut down HK-91 style pistol with a SB Tactical SOB Brace and a Vortex Optic.
Forgotten Weapons
In this short video, Ian @ Forgotten Weapons does a great job explaining just how this system works.
MouseGunner
This is one of MouseGunner’s cool x-ray renderings where he shows the MP5’s action at work. He’s done this for other weapons as well and watching the weapon operate really helps.
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This is the front of the bag – six magazine pouches, one large flat pouch to the front and the rear mounted carry handle is visible.
This is the back – you can see the shoulder strap and the carry handle at the top.
The case has a zipper at the rear of the bag and the SP5K simply slides in. This is one thing I dislike – it does not open and lie flat. Some folks may find this a plus but I prefer bags that open.
The exterior dimensions are 24.5x14x2 and I’d knock off about half and inch all the way around for the interior dimensions. It does have some padding but not a ton.
Another dislike I have is the way it holds the MP5 magazines. They slide down in the little pouches and I can’t pull them out. I need to push at the bottom to get them to slide up.
I pushed the magazines up so you can see them in this photo. Notice where the bulges indicating the actual lower part of the magazine in each pouch. In practice, the mags slide all the way down and are hard to get out. You have to press from the bottom.
On the topic of pouches, the front pouch just forward of the magazines is very tight. The bulge you see sticking out is a Mag Lula loader. While it can hold the loader, it’s really better suited for thinner items.
Okay, rounding out my complaints, the carry handle at the rear makes for an odd front-loaded unbalanced load. I don’t know why they didn’t center it.
Summary
It’s a decent entry bag and you can get it on Amazon [click here to see it]. Sure there are things I don’t like about it but does the job. I will be investigating other cases but this case is a solid performer at the price.
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I’m a creature of habit. Vortex products are solid and have a no-nonsense – “if it breaks we will fix it” – warranty. Vortex does not sponsor me so I have no reason to stick with them other than they deliver.
I knew right way this was going to be a close-in weapon with distances being typically 25 yards or less but maybe stretching out to 50 yards. It is hard to beat a red dot at those distances for rapid target acquisition. That narrowed my options down quite a bit.
A second big deal for me is to have a wide field of view but also a relatively small dot size. This combination rules out a lot of the micro dots that are out there as they are both tiny and have a 4 MOA dot size – that means the red dot will cover 4″ and 100 yards or about 2″ at 50. The micro dots are okay and I rather like them on pistols but I wanted something a tad finer on this more controllable and accurate weapon.
All paths lead me to the current Vortex Optics Crossfire red dot. It has a 2 MOA dot size, is only 2.5″ long and only weighs 5.2oz. It also has a battery life of 7,000 hours at an output setting of 5. Note the optic has 11 levels so when you have it turned up for bright light settings, you will drain the battery faster – always keep a spare battery in the case. I’ve had a couple of range sessions get messed up to do dead/dying batteries and no spares.
American Defense AD-T1-L STD Mount
The only shortcoming, if I can even call it that, with the Crossfire is its base. Vortex did their homework and include both a short base and base that can lower 1/3 co-witness with AR iron sights. The problem is that they are screwed onto the picatinny rail. If you need to get the optic off fast, that’s not going to happen as you will need a torx driver.
I do have good news – the Crossfire has the same base geometry as the Aimpoint T-1/H-1 optics. That’s the key right there – there are a lot of mounting options out there and after some digging, I have been using mounts from American Defense for over a year and they are rock solid.
By the way, make sure you get the right mount – American Defense makes there base for a variety of optics. I am using the AD-T1-L STD.
Assembling the Optic on the Mount
The good news is that this is really easy. Undo the four screws on the bottom of the Crossfire to remove the Vortex mount. Put the American Defense mount underneath it, add a bit of Blue Loc-Tite thread locker and reinstall the screws.
Use the small Torx wrench that Vortex supplies with the Crossfire to remove the four screws so you can the swap the bases. Here you can see the bottom of the Crossfire and how the American Defense mount will align.You can see the Blue Loc-Tite and the installed screws. I like to put the Loc-Tite in the holes and then install the screws. I wiped the residue away with a paper towel after I took this photo.
The Result
The result turned out really nice. The optic is just the right height that it is relatively close to the bore and I can get a good consistent cheek weld.
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In my last post, I went over the options I considered for the brace on my HK SP5K. In this post, I’ll review the three handguards I looked at – the original forearm, a US-made polymer unit with an integral hand stop and a low-profile aluminum unit.
I really have two places I shop for HK and related parts – HKparts.net and RobertRTG. So I went and checked out what they had plus I did google searches on “SP5K photos” and “MP5K photos” to see what others were using. I’m a visual guy and can scan a ton of photos very fast and then click to read the articles.
Removing the handguard is pretty much like all other HKs – pop the pin and pull down. You can see just how short that barrel is due to HK having to comply with German export laws for the pistol to be deemed “sporting purpose.” This also means you need to carefully think how to keep your fingers, notably your thumb, out of the way. You could argue training and holding the mag well but… there is a risk no matter what.
After researching for a bit, I got it down to the following three options that I could afford to try out:
Option 1: The Original Forearm
The unit that comes with the SP5K has two things going for it – the hand stop and the muzzle guard. The little indentations you see on the sides are actually thumb rests. From a safety perspective, this seemed like the best but I wasn’t sure about how the muzzle protector would hold up over time.
Note the thumb rest of the muzzle guard area of the original SP5K handguard. The hand stop is well forward giving you plenty of grip options also.See, the actual end of the muzzle is located way down in the guard. I can’t help but wonder how the polymer will hold up over time. I’m betting HK thought about that is why they made the guard so much wider than the muzzle to allow most of the blast cone to pass by without contacting the polymer. I haven’t heard of folks having problems so HK must have designed it correctly.
Option 2: A US-made Polymer Handguard Sold by HKParts.net
The second option I decided to try was a US made “Reverse stretch forearm with hand stop” that was made for HKparts.net. It was very well, fit my SP5K great and had great room for my hand but the problem was my thumb. It wanted to go in front of the muzzle.
To be clear, it is an excellent handguard. I blame the German politicians for the abrupt barrel. If I had a muzzle device out front, this would have made an excellent forearm.
Option 3: HKParts.net’s Own Low-Profile M-Lok Unit
I removed all of the screws to install the unit just in case some wiggling was needed. I think it could have fit without my doing this but I was trying to save the finish.I knew I was in trouble. It was going to be way too short and the Ergo hand stop was going to be pushed back into a slot and not going to be able to protrude without some machining.The Ergo hand stop / barricade stop was well made. No complaints at all with that part. It installed just like any M-LOK component does.Here you can see that the Ergo’s position is constrained by the M-LOK design.Houston, we have a problem. I wear XL-sized gloves found the resulting set up way too awkward. I thought about drilling and tapping the handguard to move the Ergo forward but then I would still have my thumb flopping around.
Bottom line, this just was not going to work as much as I wanted it to. Blasted politicians.
So What Did I Do?
After trying all three out, I decided to actually stay with the original forearm. Some day in the future, I will spend the money to have a B&T barrel installed with a tri-lug adapter. I really like the B&T brake that I run on my POF-5 and will then decide on which of the handguards I want to use. So, the brace and handguard were both selected, in the next blog post, I’ll discuss the optic I went with and why.
Here she is for the moment. Note I added a QD Swivel to the mounting point on the brace.
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In the last post, I told you I bought an HK SP5K. It’s relatively heavy and begging for a brace. I don’t really feel the need to spend the money and wait to register it to be a Short Barreled Rifle (SBR) and there are actually a ton of arm brace options out there.
Option 1: The SBT5KA Brace
I have a SB Tactical SBT5A Brace on my POF-5 and really like it. I knew they made a version for the SP5K known as the SBT5KA but I was hoping for something different. Please note they are two different models of braces reflecting the different receiver end caps.
Option 2: The SOB Brace
Every time I write this product name – the “SOB” – down, I smile. SB Tactical has a ton of braces for the AR/M4 weapons family and they have evolved a ton away from the ugly original. The SOB has clean lines and I run one on my PTR PDWR. I think it looks good and has handled the .308 rounds from the PDWR just fine and feels solid too.
Needless to say, I was bummed. I had it completely installed only to find out that the guide rods on the SBPDW run right into the sides of the SP5K. Crud. I didn’t feel like figuring out all the changes that would be needed.
Installation was a breeze. Pull out the two small pins at the back, swap the old end-cap for the brace, push them together and reinsert the pins. I did make sure the recoil rod lined up and nothing was binding as I reassembled the unit.
I Did Clean and Lube The Internals
I should point out that when I removed the end cap, I went ahead and slid out the bolt group and lubricated everything. I applied Super Lube grease to the bolt body and Mobil 1 Synthetic 10w30 via a precision oiler to the rollers of the bolt and rotating surfaces. I also oiled the pins on the trigger pack while greasing the hammer face with Super Lube.
Summary
So you see I went with the SBT5KA brace. In the next post I will discuss handguards.
Note, I have to buy all of my parts – nothing here was paid for by sponsors, etc. I do make a small amount if you click on an ad and buy something but that is it. You’re getting my real opinion on stuff.
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Folks, I have thoroughly enjoyed my POF-5, which is an MP5 pistol clone, this past summer. We easily put way past 500 rounds through it with zero failures to feed or eject. All my family members and friends wanted to shoot it and we had a ton of fun. However, in the back of my head, there was a little voice saying “you need a real HK”.
Finding a Real HK
I’d talked to a few guys and the consensus was that a real HK will just go up in value even after being shot plus there are the bragging right of owning a real HK. There was one problem – HK stopped making MP5s available for civilian sales. There are definitely a lot of parts kits out there but then someone needs to pay an HK smith to assemble the subgun. I thought about doing it but I lack the experience and the tooling. Given the price $1,600-3,200 price of kits, I wasn’t about to experiment.
It turned out that HK still made a civilian pistol – the SP5K – “Sporting Pistol” 5K – that is a semi-auto version of the short MP5K submachine gun. The one catch is that it comes to the US market a tad neutered. Surprisingly, this was done due to strict German export laws and not US import laws. For me, the sad part is that the barrel is 115mm/4.53 inches long and ends abruptly at the sight block – not only is there no threading or tri-lug attachment point but the abrupt end means you can’t add one either without replacing the barrel. However, accuracy reports are excellent so at least that and reliability were still there.
Before I seriously considered buying one, I did some research:
Of course, these things aren’t cheap and they are really hard to find in stock. I hunted around online while my FFL, Scott Igert of Modern Antique Firearms, did the same. After hunting for a few weeks it dawned on me that I would need to use GunBroker. So, I started by watching auctions and seeing what stuff sold for before I started actually bidding and losing. I learned a while ago not to chase auctions – set a price and don’t go past that limit. I finally found a deal after watching and bidding for over a month.
So, the seller was Town Police Supply, located in Collinsville, VA, who goes by GunTalker on GunBroker. They had an A+ reputation with over 700 trades. I always prefer to deal with sellers that have a lot of trades. At any rate, they were great to deal with. I won the auction on 9/24/18 and it arrived at Scott’s shop on 9/25. Literally.
As you can imagine, I picked the SP5K up as soon as I could. It came in a real cool HK hard case with two 10 round magazines, a sling and a sight adjustment tool as you can see in the featured photo at the top.
Here’s the plain pistol out of the box:
In summary
So, it was definitely cool but if you know me, you also know what was going through my head – “I can customize this!” In my next blog post, I’ll talk about what I considered for braces.
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Amazon product links are at the bottom of the blog.
I’m more knowledgeable about the Soviet AK-47 than I am the German Sturmgewehr 44 (StG 44). The main reason I even known about the StG 44 is from reading about it in books that cited it as being an inspiration to Mikhail Kalashnikov and his design team. But was it really – I’ve heard some heated debates about this.
I had some time and watched this brief video where Ian McCollum of Forgotten Weapons has a Chinese Type 56 sitting next to a StG 44 as he talks. They were both on loan from the James D. Julia auction company.
Ian gave a very interesting perspective that the AK-47 was essentially designed as a more powerful replacement for the Soviet’s PPS-43 that fired the 7.62×25 Tokarev pistol round.
In constrast, the Germans were wanting a controllable automatic fire weapon that would increase the firepower of soldiers especially during tactical withdrawals. They had the German 7.92×57 bolt action K98 and the famous MG42 belt fed machine gun also in 7.92×57 but they needed something different hence the StG 44.
Now, I have no doubt Kalashnikov and his design team got ideas from the StG 44. Any good engineer would take an existing design and learn from it. The Soviets needed to build up a hero so there is a lot of myth mixed in with history so I am not sure where to draw the line myself.
The video shows you the two rifles and actually shows live firing of the two so you can see how the StG 44 was actually more controllable. I thought this was really cool because the slow motion really shows the difference.
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My wife and I were walking around downtown Dowagiac, MI, when I spotted a memorial with an odd little piece of artillery sticking out above a bush located by the intersection of South Front and Main Street.
I walked over and realized I had no idea what it was. Given it was a WWI monument, it had that “WWI Look” and the wooden steel clad wheels – even I could figure out it was a WWI piece but what was it? Somebody had spray painted part of it with some brass/bronze paint that was fading but it was actually in surprisingly good shape.
My first thought was that it was some kind of short barreled howitzer but didn’t turn up anything. I then realized it might be some type of large mortar so I searched on WWI mortar photos. Being a visual person, I can scan a ton of photos fast and I found it pretty quick. It was an early generation Imperial German 17 cm mittlerer Minenwerfer (17 cm mMW a/A) made by Rheinmetall.
These large mortars were for destroying fortifications in trench warfare. Interesting minenwerfer means “mine projector”. About 2,360 of them were made between 1913 and 1918. Only 150 were available at the start of WWI.
The minenwerfers played a critical role in destroying fortifications – notably those containing machine guns and artillery as well as clearing field obstacles such as barricades and barbed wire.
They were compact but at 525KG (about 1,157 pounds), they were difficult to maneuver in a rush.
As far as I can tell, the Dowagiac minenwerfer is a 17cm mMW a/A with the last meaning Alter Art which means it is the early model before they increased the barrel length in a newer model known as the 17cm mMW n/A – with the last part meaning Neur Art – or the “new alteration”
The next photo caught my eye due to the Rheinmetall logo that I also have on HK G3 magazines made my Rheinmentall.
The monument is for the men who lost their lives in WWI from Dowagiac and also Cass County. Note the quote “It is an investment not a loss when a man gives his life for his country”.
I can’t help but wonder how the German mortar wound up in Dowagiac. I didn’t see a plaque anywhere but hope to research it more some day. I also hope they preserve it. Unless I missed it, the mortar is standing on its own wooden wheels and it would be a shame if it fell.
In case you are interested, here are some great resources to learn more about the 17 cm mMW a/A:
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